As the core of magnetic storage and magnetic detection technologies, a magnetoresistance effect having significant effect and sensitive magnetic field sensitivity is always a goal to be sought in the magnetic storage industry. Currently developed and applied giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) devices are mainly based on magnetic metal materials. Semiconductor materials such as silicon (Si) are main stream materials in information industry. In view of the role they currently play in information industry, if these main stream semiconductor materials are utilized to achieve significant giant magnetoresistance devices at room temperature, a magnetoresistance device will be conveniently integrated with a semiconductor device and technology, so as to propel traditional semiconductor micro-electronics industry to upgrade toward a magnetoelectronic industry, thus having great significance.
Traditional giant magnetoresistance devices (see, e.g. “Journal of Applied Physics”, No. 69; 1991, page 4774) and tunneling magnetoresistance devices (see, e.g. “Nature Materials”, No. 3, 2004, from page 862) have excellent sensitivity at low magnetic field, small operating voltage and power consumption. GMR device consists of (magnetic material/non-magnetic material) multilayer film, such as (Fe/Cr)n multilayer film; and TMR device consists of a sandwich structure of magnetic metal/insulating layer or potential barrier/magnetic metal, such as Fe80Co20/MgO/Fe70Co30 structure. These magnetoresistance devices have a resistance change up to the order of 10%˜100% under a magnetic field of 10 Oe which is excellent sensitivity at low magnetic field. However, they have very remarkable disadvantages. Firstly, they have isotropic magnetoresistance, and can not be used for sensing the direction of magnetic field. Secondly, their magnetoresistance generally saturates under small magnetic field, therefore they can not be used for sensing medium and strong magnetic fields. Thirdly, the manufacturing of these magnetoresistance devices needs transition metals, rare earth metals and the like, which not only leads to high cost, but also makes the manufacturing process incompatible with silicon process. The silicon process generally does not use transition metals as much as possible, since a family of transition metals may cause un-controllable doping of silicon, and reduce performances of silicon electronic elements.
In 2009, Delmo et al. invented a pure Si-based magnetoresistance device (“Nature”, No. 457, 2009, page 1112). This device realizes magnetoresistance of 103% under 300K room temperature and 3 T magnetic field. This magnetoresistance value is 2 orders of magnitude higher than normal magnetoresistance in Si, which brings about a hope for realizing practical Si-based magnetoresistance devices. However, this device has low sensitivity at small magnetic fields and requires high working voltage (100V level) and high power (0.1 W˜1 W), thus still falls far short of practical industrial application. In the same year, Schoonus et al. also found remarkable magnetoresistance effect in pure Si and realized 103% of magnetoresistance under 1 T magnetic field (“Journal of Physics D: Applied Physics”, No. 42, 2009, page 185011). However, similarly to Delmo, this device has high operating voltage and high power consumption, even higher than those of Delmo's device, hence its practical application value is very limited.
Other than Si-based giant magnetoresistance materials, other systems can also realize remarkable magnetoresistance characteristic and have low field sensitivity and low power consumption, such as a magnetoresistor of InSb/Au structure which was invented by Solin et al. (“Science”, No. 289, 2000, page 1530). This kind of magnetoresistance device consists of a central aurum disk and an InSb circular ring surrounding the aurum disk. This structure can realize 100% apparent magnetoresistance performance under 0.05 T magnetic field, which approximate performances of commercial giant magnetoresistance and tunneling magnetoresistance devices. Despite having excellent performances, this device has a complex structure, which results in complicated manufacturing process and raw materials of high cost, as well as difficult device miniaturization. These disadvantages limit its large scale application.